Mei Xiang, the National Zoo's giant panda, gave birth to a panda cub Sunday night — her second — after five false alarms in a row.

The new cub was born at 10:46 p.m. Sunday. The zoo announced the news about four hours later.

Zoo officials said they believed only one cub had been born, but they should know by early Monday if the cub has a twin.

"Mei Xiang is behaving exactly the same way she did when Tai Shan was born," chief veterinarian Suzan Murray said in a statement.

"She is cradling her cub closely, and she looks so tired, but every time she tries to lay down, the cub squawks and she sits right up and cradles the cub more closely. She is the poster child for a perfect panda mom," she said.

Vets used sperm collected and frozen from Tian Tian in 2005. That might have been a particularly good year for him, as 2005 was also the year that brought us Mei Xiang and Tian Tian's first cub, Tai Shan.